The purpose of this activity is for students to find sums when one addend is nine. Students represent sums on the 10-frame to encourage them to use the structure of a ten. During the Launch, the teacher demonstrates playing a round of the game. It is important to let students discover patterns as they play the game. For example, when finding the sum of , some students may represent each addend on a separate 10-frame and count to find the sum. Other students may use the associative property and move one counter from the 5, and add it to the 9 to make a ten.

Students may generalize that when they take one from an addend to make 10, the sum has one less one than that addend. When students build this understanding, they may no longer need to show their thinking on the 10-frame and can just write an equation. By repeatedly making the 10 by taking one from an addend, students may see and use the structure of 10 to add on (MP7, MP8).

• “¿Qué patrones observaron cuando jugaron el juego?” // “What patterns did you notice as you played the game?” (I saw that a  expression can be written as a expression. You can take 1 from the other addend. The 9 goes up by 1, and the other addend goes down by 1.)
• “Podemos escribir la ecuación  para representar el hecho de que las expresiones son iguales” // “We can write the equation to represent that the expressions are equal.”

The purpose of this activity is for students to solve addition story problems in which one addend is close to 10. Students may use any method or representation that makes sense to them. During the Synthesis, the double 10-frame is used to visually show decomposing one addend to make 10 with the other (the associative property).

• Reread the second problem.
• Invite previously identified students to share in the given sequence.
• “¿Qué hizo _____ para representar el problema?” // “What did _____ do to represent the problem?”
• Record each method with an equation.
  • 6 + 8 = 14
  • 8 + 6 = 14
  • 6 + 4 = 10, 10 + 4 = 14
  • 8 + 2 = 10, 10 + 4 = 14